Trichilemmal horn: case presentation and literature review

Onycholemmal Horn: An Exceedingly Rare Subungual Tumor

The onycholemmal horn is an exceedingly rare subungual tumor characterized by trichilemmal-like keratinization pattern. The only previous instance of onycholemmal horn dates back to 1983 when Haneke reported a keratotic subungual tumor clinically and histologically comparable to a trichilemmal horn. No other case of this condition has been reported so far. We present the case of a 72-year-old female patient, with a history of a slowly growing tumor originating from the nail bed epithelium of the left thumb. The lesion was surgically removed, and pathological examination was consistent with the diagnosis of an onycholemmal horn. Additionally, this study aims to elucidate the correlation between the onycholemmal and trichilemmal keratinization.

Pilomatricomal Horn

We describe a pilomatricomal horn on the right arm of a 39-year-old man. Although initially the tumor was clinically thought to be a verruca vulgaris, the microscopic features were similar to those found in classic pilomatricoma, except for the epidermal location and the presence of a cutaneous horn. Light microscopy showed replacement of the epidermis by basaloid cells, with masses of cornified material containing shadow cells that formed a cutaneous horn. Whereas classic pilomatricoma is confined to the deep reticular dermis or subcutis, the present case represents a unique heretofore unreported epidermal variant of pilomatricoma that pathologists should be aware of to differentiate it from malignant epidermal tumors.

Gigantic cutaneous horns of the scalp: lesions with a gross similarity to the horns of animals: a report of four cases

Gigantic cutaneous horns, grossly similar to the horns seen in animals, are exceedingly rare in humans. After finding one case in practice, we searched our departmental files for similar cases and examined them grossly and microscopically. Four cases were identified. All occurred as solitary lesions in older women on the parietal-occipital region of the scalp. They had a growth history of up to 30 years; the women hid these horns in their hair. Grossly, the horns were yellow-grey, and there were shallow furrows running along the length of the horns. The length ranged from 17 to 25 cm, and the width was up to 2.5 cm. All four lesions showed similar histologic changes. Microscopically, the gigantic horns consisted of a mixture of squamous epithelial cells and tricholemmal keratinized debris. In one case the base of the horn was directly connected with a mass composed of benign tricholemmal cysts of the scalp. Mitoses were common, but atypical mitoses were not observed. The nuclei of the squamous cells were bland without pleomorphism, hyperchromasia, or atypia. Follow-up of all patients was uneventful: all patients were well and without signs of recurrence or metastasis 2-15 years after the surgical excision. Gigantic cutaneous horns are rare and benign. We think that they represent an extremely well-differentiated variant of proliferating tricholemmal tumor with an unusual and remarkable gross pattern.